The invention relates to highway trailers and more particularly to trailer vehicles of selectively variable width.
It is often desirable to modify the platform width of a transport vehicle, particularly for transporting exceptional loads of large transverse dimensions, such as public works machines.
In many States, the regulations for exceptional transport limit the admissible load per axle or per axle line as a function of the transverse track of the vehicle. Providing that the track is widened at the same time as the platform, the most appropriate wheel track can be adopted for the transport of a given load. Moreover, once the transport has been completed, the vehicle can then be modified to a smaller track and possibly comply with the provisions of the law whereby the return journey may be achieved under normal conditions and at a higher speed, whereas the outward journey with an outsize vehicle must be undertaken under much more restrictive conditions, with forerunning and trailing vehicles.
Gooseneck trailers have been proposed in which a side frame and ground contacting wheels carried by that frame are transversely movable with respect to a main frame. But these vehicles have considerable defects which make their commercial interest doubtful. Moving the side frame aside causes the appearance of a gap near one side of the platform, i.e. in a region where are placed the supports of the most frequent loads (caterpillar tracks or wheels of public works equipment particularly).
Moreover, this solution cannot be used on vehicles fitted with steerable wheels (which is the case with high tonnage trailers) because of the steering diagram changes which it involves.
There is also known (French Pat. No. 1,303,042) a towed road vehicle whose drawbar drives a linkage for steering the first line of wheels and drives the movable members of two symmetric steering jacks associated with two corresponding jacks which steer the wheels of the last line of the trailer. Such steering system cannot be transposed to the case of a variable width trailer since for each track width the steering diagram would have to be modified.
It is an object of the invention to provide a highway trailer, of adjustable width over part at least of its length, provided with steerable wheels which overcomes the above disadvantages.
According to the invention, a highway trailer of selectively variable width has two side structures, each having at least one longitudinal row of axles provided with ground contacting wheels; transverse means connecting said side structures, enabling movement of said side structures in the direction transverse to the direction movement of the trailer and including a steering crossbeam; motor means for moving the side structures between an inner position corresponding to minimum width and track of the trailer and an outer position corresponding to maximum width and track; a hitching member rotatably connected to said transverse means and adapted to be connected to a driving vehicle; and steering means for some at least of said axles, comprising a pair of fluid steering jacks located symmetrically each between said steering cross-beam and said hitching member, whereby the fluid compartments of said jacks are subjected to variations in volume responsive to rotation of the steering member; and at least one pair of auxiliary fluid jacks each connected by pipe means to a corresponding one of said steering jacks and each located between one of said side structure and a steering arm of a corresponding one of said axles.
The invention will be better understood from a consideration of the following description of particular embodiments thereof given by way of non-limiting examples. The description refers to the accompanying drawings .